FiatECUScan. (http://fiatecuscan.net/) is probably your best bet. Free version with do basic engine stuff on most cars. The paid for version will do engine, airbags, abs, etc (read vehicle coverage notes) and is about as near to dealer (examiner) diagnostics you will get for a fraction of the cost of the other garage pro kit out there costing 1000EUROS or more.
Word of warning. Be careful when bying ELM interfaces. So the these clone from Chine are more trouble that they are worth. The latest version of ELM is 1.4! (no such thing as 1.5).
Personally I would recommend Gendan (http://www.gendan.co.uk). They can supply latest ELM 1.4 USB interface. There are plenty of other good companies out there as well.
Another word of caution. With FiatECUScan it is currently NOT recommended to use a BlueTooth ELM device but to stick with cable versions.
Version 2.3 onwards of FiatECU scan restricted some functions that were previously free. Older cars will be OK with KKL/ELM for airbags and ABS but more modern vehicles will require CAN connection (supported only with ELM interface).
Original poster does not specify a verhicle/vehicles so he/she will have to research FiatECUScan themselves.